Effects of Leonotis leonurus aqueous extract on the isolated perfused rat heart

Abstract

The use the aqueous decoction of Leonotis leonurus (L. leonurus) (Ll) R. Br. (Lamiaceae) in the treatment of hypertension (HPT) in traditional medicine is well documented. The effect of the aqueous extract of LI on the blood pressure (BP) and heart rate (HR) has been investigated in normotensive rats. The aim of this study was to investigate the effect of Ll aqueous extract on the in isolated perfused rat heart (IPRH). Hearts were excised from male Wistar albino rats weighing 250-350g, aged less than 6 months. They were perfused at constant flow using the modified Langendorff perfused model of the heart. Effects of adrenaline on the left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), heart rate (HR), cardiac work (CW) and coronary perfusion pressure (CPP) were compared to that of Ll. Adrenaline (1µM) significantly (p<0.05) increased the LVSP by 40.6%, the LVDP by 43.9%, the HR by 22.5% and the CW by 89.4%. Ll (1.0 mg/ml and 2.0 mg/ml respectively and significantly (p<0.01) increased the LVSP by 25.36 and 14.91, the LVDP by 29.40 and 14.88. Ll (1.0 mg/ml and 2.0 mg/ml) significantly produced a negative chronotropic effect. Both adrenaline and Ll aqueous extract did not have any significant effect on the LVEDP. Adrenaline resulted in positive inotropic and chronotropic effects. At low concentrations Ll produced a positive inotropic and a negative chronotropic effect. At the concentration of 2.0mg/ml Ll decreased all parameters to zero. At higher concentrations higher than 2.0mg/ml, Ll seemed to have toxic effects on the heart.